FCETAL NUTRITION: THE PLACENTA 447 



network are penetrated by the vessels of the villi. In this way, 

 according to Duval, the labyrinth is formed. In it the maternal and 

 the fatal blood are separated by the endothelium of the uterine 

 capillaries, a cellular layer (considered foatal by Duval and maternal 

 by Heinricius) which later disappears, the syncytium, mesoblast, and 

 fostal capillary walls. 



At places, however, the villi come directly in contact with 

 maternal blood, especially at the "green border" of the placenta, 



FIG. 125. The labyrinth and the green border of the placenta of the dog at 

 the fortieth day of pregnancy. To the right are two lobules of the 

 angioplasmode which have reached the stage of complexity of the 

 labyrinthine lamellae : to the left is the green border, the cavities of 

 which, normally filled with blood, are indicated by a cross. (From Duval's 

 " Le Placenta des Carnassiers," J<nn-. <l<' /'. \n<tf. ( <l>- tn /'//>/*., 1893.) 



1, 2, and 3, Basal lamellae of the green border ; 4, basal lamella of lobule 



of labyrinth. 



which forms a characteristic appearance in some of the Caniivora. 

 In all the members of the order, larger or smaller maternal 

 haemorrhages occur at an early period after the attachment of the 

 blastodermic vesicle. The effusions vary in size and position. In 

 the dog they occur regularly along the margins of the placental zone, 

 and form the Iwditrr />-///; in addition smaller luemorrhages take 

 place into the substance of the placenta, and form the "green 

 pockets," which may be isolated or joined to the green border by 

 bridges (Fig. 125). In the cat the haemorrhages occur in irregular 

 positions and do not assume the green colour typical of the dog. 

 Indications of a green border are present in the earlier stages, but 



